Elastic member and paper feeding roller using same

ABSTRACT

A paper feeding roller having a high paper feeding capability, excellent wear resistance and weatherability, and which is capable of being easily produced. The invention provides a paper feeding roller in which an outer peripheral surface of the roller is surrounded by a laminar elastic member comprising a hydrogenated polystyrene-based thermoplastic elastomer, having a plurality of outwardly protruding projections on a surface of said member and the elastic member satisfies at least one of the following requirements: containing an inorganic filler, containing an additive consisting of a wear-resistant resin, and being modified by irradiation with radiation.

CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority from Japanese Serial No. 2002-165270 filed Jun. 2, 2002.

BACKGROUND OF THE INVENTION

[0002] It is known that various types of paper feeding rollers are used for feeding printing papers, recording sheets, bank notes and the like, in the field of various imaging apparatuses such as copying machines, printers and facsimiles, automatic teller machines (ATM), cash dispensers (CD) and the like. For the paper feeding rollers for imaging apparatuses in particular, three important requirements should be satisfied to cope with the trend of advancement in functions of apparatuses, speeding up of the processing, diversification of paper and the like. That is, a paper feeding roller should have a high paper feeding capability, an excellent rear resistance and weatherability.

[0003] With respect to the paper feeding capability, it has become necessary to stably feed a paper heavier per unit area than ever, in accordance with the development of feeding a large-size paper. It is thought that a high paper feeding capability, prevents double feeding of papers. That is, when a feeding roller is activated, a paper should be pressed to the feeding roller with certain force by a pressing member used in combination with the feeding roller. In this instance, if the feeding roller has a low feeding capability, the paper is not effectively fed and no paper may be fed if the pressing force of the pressing member is weak. On the contrary, if the pressing force is strong, the frictional force between papers becomes too strong and causes a double feeding of papers. If the feeding roller has sufficiently strong feeding force, the pressing force of the pressing member also becomes strong. Therefore, even if the frictional force between papers becomes strong, a stable paper feeding is ensured without causing the double feeding problem.

[0004] A high paper feeding capability has a relation also to the wear resistance of a paper feeding roller. Recently, it has become common that a large amount of papers are processed in a shorter time than before. With this tendency, paper feed rollers, which could endure the feeding of a small amount of papers at a low speed, become worn at an early stage after the start of use. Further, low price papers and coated papers containing a large amount of resin are being used these days. This fact also accelerates the wearing of the feeding roller. Consequently, it has become necessary to develop a paper feeding roller which will not wear or be degraded in the paper feeding capability even after a large amount of, and various kinds of, papers have been fed.

[0005] Further, ozone is often generated from an imaging apparatus at the time of a fixing process. Therefore, a paper feeding roller should have ozone resistance. Because an imaging apparatus is used in various environments such as in a high temperature and humid area, the feeding roller should have resistance to high temperature and humidity. In this specification, the word “weatherability” is used to include ozone resistance, resistance to high temperature and humidity, light fastness, etc. The paper feeding roller is also required to be produced easily by a simple way.

[0006] However, the conventional paper feeding rollers do not satisfy the above requirements.

[0007] To obtain a high feeding capability, a high frictional force is generally required. In order to realize the high frictional force for conventional feeding rollers, a rubber material with a low degree of hardness, i.e., a low elastic modulus rubber, has been used as the outer peripheral member. The generally used rubber material contains, as a softening agent, a large amount of process oil mixed in a polynorbornene-base rubber. However, the conventional feeding rollers suffer from the problem of staining papers by exuded process oil during use or the transfer of the process oil to papers, causing slippage and reduction of the paper feeding capability.

[0008] There are some paper feeding rollers, which use ethylene-propylene-diene copolymer rubber (EPDM) as the outer peripheral members. For example, Japanese Unexamined Patent Publication (Kokai) No. 9-254275 discloses a rubber roller characterized in not mixing a filler such as titanium oxide, silica or carbon black with oil-added EPDM rubber, or in case of mixing the filler, the filler is mixed in an amount of 15 parts by weight or less into 100 parts of the rubber component. However, because the rubber rollers use the EPDM rubber as a base, they must use process oil as a softening agent to obtain workability and a low degree of hardness. Therefore, these rollers are not free from the problems caused by the process oil, such as staining of papers and the occurrence of slippage. Further, because the EPDM rubber must be vulcanized prior to being molded, a high temperature treatment is necessary, causing inconveniences in productivity or production capacity. In addition, a problem of adhering paper powder to the roller surface during the use of a long time occurs, leading to the reduction in the paper feeding capacity. This problem is applied also to the norbornene base rubbers above.

BRIEF SUMMARY OF THE INVENTION

[0009] The present invention aims at solving the above-mentioned drawbacks of the prior arts. The present invention relates to an elastic member and a paper feeding roller. More particularly, it relates to an elastic member and a paper feeding roller used to allow sheet-by-sheet feeding of papers from stacked sheet-like papers in an imaging apparatus such as copying machine, printer and facsimile. The paper feeding roller of the invention has a high paper feeding capability, excellent wear resistance and weatherability. It maintains these features over a long use, without causing the problems of staining paper, slippage and the reduction of paper feeding capability due to paper powder adhering, and is capable of being easily produced. Hereinafter, a sheet-form material used generally in the imaging apparatus, such as a printing paper and recording paper is described as “paper” or “sheet”.

[0010] Therefore, the object of the present invention is to provide a paper feeding roller which has a high paper feeding capability, excellent wear resistance and weatherability, which maintains these features for a long time, without causing the problems of staining paper, slippage and the reduction of paper feeding capability due to paper powder adhering, and which is capable of being easily produced.

[0011] A further object of the invention is to provide a paper feeding roller, which allows sheet-by-sheet feeding of papers from stacked sheet-like papers in an imaging apparatus such as a copying machine, a printer and a facsimile.

[0012] A still further object of the invention is to provide an elastic member used for the paper feeding roller for feeding paper.

[0013] The inventors studied hard to achieve the above objectives. They found that the three requirements of the paper feeding capacity, the wear resistance and weatherability can be satisfied at the same time by covering the outer peripheral surface of the roller with a layer of an oil-free elastic member, and by providing a plurality of protrusions on the surface of the layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a perspective view of an embodiment of the paper feeding roller of the invention.

[0015]FIG. 2 is a sectional view showing the structure of the paper feeding roller of FIG. 1.

[0016]FIG. 3 is a perspective view of an embodiment of projections provided on the surface of the elastic member of the invention.

[0017]FIG. 4 is a perspective view of another embodiment of projections provided on the surface of the elastic member of the invention.

[0018]FIG. 5 is a sectional view of an embodiment using the paper feeding roller of the invention.

[0019]FIG. 6 is a sectional view of another embodiment of using the paper feeding roller of the invention.

[0020]FIG. 7 is a sectional view of still another embodiment of using the paper feeding roller of the invention.

DETAILED DESCRIPTION

[0021] According to one aspect of the present invention, there is provided an elastic member used in paper feeding, characterized by comprising a hydrogenated polystyrene-based thermoplastic elastomer, having a plurality of outwardly protruding projections on a surface of the elastic member, and satisfying at least one of the following three requirements:

[0022] (1) containing an inorganic filler,

[0023] (2) containing an additive consisting of wear-resistant resin, and

[0024] (3) being modified by irradiation with radiation.

[0025] According to another aspect of the present invention, there is provided a paper feeding roller having an elastic member, wherein the elastic member is characterized by comprising a hydrogenated polystyrene-based thermoplastic elastomer, having a plurality of outwardly protruding projections on a surface of the elastic member, and

[0026] satisfying at least one of the following three requirements:

[0027] (1) containing an inorganic filler,

[0028] (2) containing an additive consisting of wear-resistant resin, and

[0029] (3) being modified by irradiation with radiation.

[0030] As has been mentioned, the elastic member of the present invention is characterized by comprising a hydrogenated polystyrene-based thermoplastic elastomer, having a plurality of outwardly protruding projections on a surface of the elastic member, and satisfying at least one of the following three requirements:

[0031] (1) containing an inorganic filler,

[0032] (2) containing an additive consisting of wear-resistant resin, and

[0033] (3) being modified by irradiation with radiation.

[0034] The elastic member can be used for various applications due to its characterizing feature, and can be used particularly advantageously for the feeding of paper. Therefore, the elastic member can be used as a component for the paper feeding roller used in an imaging apparatus. The elastic member can be used also as a separation pad.

[0035] The elastic member of the invention can be used in various forms depending on the usage. Particularly useful forms are a rectangular sheet, a cylindrical tube or pipe, an endless belt or the like. It may be used in a form of a plate. The elastic member can be called “a laminar elastic member” due to its thickness, as explained and defined later. The elastic member of the invention may have a form of a solid cylinder or other form as a variation. Details of the elastic member are explained below, but it can be optionally varied within the scope of the invention.

[0036] The paper feeding roller of the present invention comprises generally a core (also called a shaft) and an elastic member of the invention. The elastic member is a laminar elastic member surrounding the outer peripheral surface of the core. FIG. 1 shows an embodiment of a preferred paper feeding roller 10, comprising a core 1 and a laminar elastic member 2 surrounding the outer peripheral surface of the core 1. The elastic member 2 has a plurality of characteristic protrusions 3 formed on its surface. The structure of the elastic member is easily understood from the sectional view shown in FIG. 2.

[0037] The core 1 provided in the center of the paper feeding roller 10 comprises a cylindrical member having a predetermined diameter depending on the usage, just as conventional paper feeding rollers. The member may be produced from, although not limited to, metal such as iron, stainless steel and aluminum alloy, or plastic material such as polycarbonate, polypropylene, polyamide and polystyrene. The core 1 may have a hollow structure as illustrated, so as to be light in weight. Further, the core 1 may be a modified solid cylinder in which a portion of the curved face is cut off to create a flat, when the paper feeding roller of the invention is used for a feeding mechanism of a separation pad type, as mentioned below.

[0038] The laminar elastic member 2 is fitted to the cylindrical core 1 as mentioned above. The “laminar elastic member” has a sufficient thickness to function as a paper feeding roller. Therefore, it refers to an elastic member having a laminar, film or sheet-like form depending on its thickness. The thickness of the elastic member may be widely varied in accordance with the position used or the usage of the feeding roller. The thickness is generally about 0.1 to 3 mm, preferably about 0.2 to 2 mm and more preferably about 0.25 to 1.5 mm.

[0039] The elastic member 2 can be fixed in an optimum way to the cylindrical core 1, depending on the characteristic feature and the size of the elastic member. Because the elastic member of the invention has an extremely increased frictional force to paper or film, it is difficult to stop slipping of papers between layers by expanding the elastic member to simply fit the expanded member to the core, as is generally adopted. According to the invention, the elastic member is fixed to the core by an adhesive layer, by a mechanism for mechanically absorbing the shearing force between the inner surface of the cylindrical elastic member and the outer peripheral surface of the core, by an injection molding cylindrical member on the outer peripheral surface of the core, or by another method. Examples of the adhesive used for the adhesive layer are, although not limited to, an acrylic adhesive and a cyanoacrylate adhesive. In place of the adhesive, a two-sided tape, such as an acrylic, pressure-sensitive two sided tape may be used. Although not shown in FIGS. 1 and 2, an adhesive tape is used between the core 1 and the elastic member 2.

[0040] The method of expanding the elastic member, to simply fit it to the core, may cause problems as mentioned above. But the shearing force caused by the high frictional force can be obtained by providing similar projections in the back surface of the elastic member and in the core surface. The fixing projections may be gear-like projections provided axially on both of the elastic member and the core. Otherwise, each of the projections may have a quadrangular pyramid form, or a roughened surface obtained by an electric-discharge machining or a flame spray coating process. The height and the pitch of the projection are normally within the range between about 0.1 and 1.0 mm, preferably between about 0.2 and 0.8 mm, and more preferably between about 0.3 and 0.5 mm.

[0041] When the elastic member is used in a form of a rectangular sheet or an endless belt, a reinforcing member is preferably provided on the back surface (the surface opposite to the projection-provided surface) of the elastic member to maintain the form. Cloth or a non-woven cloth is suitably used as the reinforcing member.

[0042] The advantageous functions of the paper feeding roller of the invention are largely derived from the composition, shape, etc. of the inventive elastic member covering the outer peripheral surface of the roller.

[0043] First, the elastic member of the invention should comprise a hydrogenated polystyrene-based thermoplastic elastomer. The thermoplastic elastomer exhibits good rubber elasticity and relatively high frictional force at the temperature the roller is used. Further, because the thermoplastic elastomer has no double bond at the elastomer part, it is excellent in weatherability to ultraviolet rays and ozone, in contrast to the conventionally used polynorbornene and the like.

[0044] The hydrogenated polystyrene-based thermoplastic elastomer, which is suitable for producing the elastic member, is a hydrogenated product of a block copolymer comprising at least one styrene block and a block which is based on at least one conjugated diene compound, i.e., a hydrogenated polystyrene-based block copolymer. The styrene block is suitably used in an amount of about 10 to 70% by weight on the basis of the total amount of copolymers. An example of the conjugated diene compound is a random copolymer of polybutadiene, polyisoprene or one or more of the foregoing and ethylene. Further, a part of the diene compound may be modified by a functional group such as a maleic group, a carboxyl group and an epoxy group. The hydrogenated polystyrene-based block copolymer may be used singly or two or more copolymers may be blended or copolymerized.

[0045] The polystyrene-based block copolymer may be used at various molecular weights. The average molecular weight of the block copolymer is, although not limited to, normally about 100,000 to 400,000. If necessary, the weight can be greater or smaller than this range.

[0046] The hydrogenated polystyrene-based block copolymer includes, but is not limited to, tri-block copolymer (SEBS) of styrene-styrene-butylene-styrene, tri-block copolymer (SEPS) of styrene-ethylene-propylene-styrene, di-block copolymer (SEB) of styrene-styrene-butylene and di-block copolymer (SEP) of styrene-styrene-propylene. When the mechanical strength of the elastic member is considered, the tri-block copolymers of SEBS, SEPS and so on are particularly preferably as the styrene-based block copolymer.

[0047] The hydrogenated polystyrene-based block copolymer may be used in various volumes in the elastic member. But in order to obtain satisfactory paper feeding capacity, the block copolymer is preferably used in an amount of normally at least 20% by weight on the basis of the total weight of the elastic member. More preferably, the amount is 30% by weight or more, and most preferably 50% by weight or more. The upper limit of the amount of the block copolymer is, although not limited, normally about 100% by weight.

[0048] Second, the elastic member should have a plurality of outwardly protruding projections in its surface. Due to the presence of a plurality of the projections in the outer peripheral surface, the paper feeding capacity is still further increased. This is because the paper powder, which is produced by the friction between a large amount of papers during long use of the roller, can be moved into the minute spaces (recesses) between projections without stacking on the roller surface, whereby the good paper feeding capacity seen at the beginning of use can be maintained.

[0049] The projections can protrude from the outer peripheral surface of the elastic member in various shapes, sizes and densities between projections. A suitable projection may be, although not limited to, a cylindrical projection 3 protruded from the surface of the elastic member 2 as shown in FIG. 3. Further, a projection 3 of a quadrangular pyramid form may protrude from the surface of the elastic member 2, as shown in FIG. 4. Another suitable projection may be one which resembles to the hook of a hook-and loop fastener, such as a mushroom-like projection. The surface of the projection may be flat as shown in drawings, spherical or semi-spherical. The projection is normally constituted from a single material, but it may have a composite structure to improve its strength or flexibility. For example, the center of the projection may be formed of a core material same as that of the elastic member, and the periphery of the core may be coated with a more flexible material.

[0050] Each of the projections normally has the same form. If necessary, however, projections of different forms may be combined. Similarly, although same height projections are normally used, different height projections may be combined. Further, although projections are normally arranged with the same density of projections, they may be arranged to have different densities depending on positions.

[0051] In a paper feeding roller of a separation pad system as shown in FIG. 7, the performance required differs by the position of the roller. The load imposed to the roller differs by positions, i.e., the position where the roller does not contact paper, the pick up position where the roller first contacts the paper, the regular range position where a paper feeding is stably carried out, and the position where paper is delivered to a next nip roller. Accordingly, the nature of the elastic member required for a paper feeding roller also differs by the position of the roller. At the pick up position and the position where paper is delivered to a next nip roller, shearing stress acts on the roller and, therefore, shearing strength is required on the surface of the roller. At the regular range position where a paper feeding is stably carried out, frictional force is required for stable paper feeding. According to the present invention, because the shapes and positions of the projections can be freely changed, the optimum paper feeding roller can be structured. Consequently, it is possible to increase the contacting area and the apparent roller strength by increasing the arrangement density and the sectional area of the projections. If necessary, projections of different heights may be provided on the surface of the elastic member, to obtain technical effects different from the case where same height projections are provided, such as an improvement in durability of the projections.

[0052] The size of the projection may be varied widely depending on the kind of the paper feeding roller. For example, the height of the projection is normally about 0.15 to 1.5 mm, preferably about 0.254 to 1.27 mm, and more preferably about 0.3 to 0.9 mm. Regarding the size of the sectional area of the projection is, when the section is circular as shown in FIG. 3, the diameter of the base of the projection is normally about 0.076 to 0.76 mm, preferably about 0.1 to 0.5 mm, and more preferably about 0.15 to 0.3 mm. The sectional area of the projection should be constant to prevent a change in characteristic features caused by wearing. However, a frustum form is preferred to maintain the bending strength of the projection. In that event, the ratio of the area between the end portion and the base portion is normally about 1.0 to 6.0, preferably about 1.1 to 4.0, and more preferably about 1.2 to 3.0. The arrangement density of the projection is normally 100 pieces/cm² or more, preferably about 200 to 1,200/cm², and more preferably about 300 to 1,000/cm².

[0053] The multiple projections can be formed on the surface of the elastic member by various ways. For example, the method shown in the applicant's International Publications WO 97/32805 and WO 00/20210 may be used. In practicing the present invention, the projections disclosed in these international publications may be advantageously used.

[0054] Third, the elastic member should satisfy at least one of the following three requirements: (1) containing an inorganic filler, (2) containing an additive consisting of a wear-resistant resin, and (3) being modified by irradiation with radiation. These requirements greatly contribute to improving the wear-resistance of the hydrogenated polystyrene-based thermoplastic elastomer constituting the elastic member. Further, the requirements contribute to significant enhancement of the paper feeding capability although the mechanism has not yet been fully clarified.

[0055] As the inorganic filler, various kinds of inorganic fillers used conventionally for reinforcing rubber can be used. Proper fillers include, but are not limited to, metallic oxide such as silica, titanium oxide and alumina, hollow fine balls such as carbon black, clay, talc, mica and glass beads, ceramic fibers, aluminum hydroxide, barium hydroxide and calcium carbonate. Among the inorganic fillers, silica, alumina, carbon black, ceramic fibers, etc. have a particularly strong effect on improving the paper feeding capability. Silica is most suitable in terms of the dispersibility to the hydrogenated thermoplastic elastomer, wear resistance, quality stability and costs.

[0056] The silica and the other inorganic fillers may be used in various general forms, as long as they do not give adverse effect to the operational advantage of the invention. Proper forms of the fillers include balls, fiber pieces, flakes and indefinite forms. These fillers may be coated on their surfaces, if necessary, for improving their characteristic features or provided with a surface treatment.

[0057] The inorganic fillers may be used in various particle sizes. Normally, they are used with a size of about 30 μm or less, and preferably about 20 μm or less, in view of workability, dispersibility, and the relationship between the amount to be added and the effect for enhancing the feeding capability.

[0058] The inorganic filler may be added in various amounts depending on the desired effects or the like to the hydrogenated thermoplastic elastomer. The amount of the filler to be added is normally about 100 parts by weight or less, preferably about 1 to 50 parts by weight, and more preferably about 3 to 30 parts by weight, on the basis of 100 parts by weight of the hydrogenated thermoplastic elastomer.

[0059] A wear-resistant resin may be used as an additive depending on necessity, in the elastic member of the invention. The additive is added to the hydrogenated, polystyrene base thermoplastic elastomer, and dispersed, to simultaneously realize a high paper feeding capacity over a long use and excellent wear resistance. The wear-resistant resin to be used is not limited as long as it has good solubility in the hydrogenated thermoplastic elastomer, and imparts the paper feeding roller with good wear resistance without giving any adverse effect to the physical properties of the roller. Examples of proper wear-resistant resins include, but are not limited to, a thermoplastic urethane resin, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methacrylate copolymer and an ionomer resin wherein a metallic ion is bonded to the carboxyl group of the copolymer, thermoplastic polyester resin and thermoplastic polyamide resin. These resins may be used singly or in a combination of two or more resins. Organic fillers of hollow, bulky, fiber-like, powdered or granular form or various vulcanized rubbers may be used in place of the wear-resistant resin, or in combination with the resin.

[0060] Particularly proper among the wear-resistant resins mentioned above is a thermoplastic polyurethane resin having excellent wear resistance. A preferable proper thermoplastic polyurethane resin is a soft thermoplastic polyurethane resin, which has a hardness of about 90A or less measured by a spring type hardness scale, according to JIS K6301 standard. The most preferred thermoplastic polyurethane resin is a soft thermoplastic resin of which polyol part comprises polycarbonate and which has a hardness of about 90A or less, preferably about 80A or less, because such a polyurethane resin greatly improves resistance to hydrolysis.

[0061] The thermoplastic resin and the other wear-resistant resin can be added to the hydrogenated thermoplastic elastomer, in various amounts depending on the effects desired and the like. The amount of the wear-resistant resin to be added is normally about 20 to 150 parts by weight, and preferably about 21 to 70 parts by weight, based on 100 parts by weight of the hydrogenated thermoplastic elastomer.

[0062] Inorganic fillers and the thermoplastic polyurethane can be mixed into the hydrogenated thermoplastic elastomer by various methods. For example, the hydrogenated thermoplastic elastomer, inorganic filler and thermoplastic polyurethane are dried, fed to a heating and mixing machine, such as a mono-axial extruder, a bi-axial extruder, a Banbury mixer, a Brabender and a kneader, and blended. If necessary, the materials may be pelletized so as to be easily processed.

[0063] Following the blending process, or after the pelletizing process, the materials are transferred to the process of forming elastic members. During the forming process, projections are provided on the surface of the elastic member. The forming process can be advantageously carried out by the methods shown in International Publications WO 97/32805 and WO 00/20210, cited previously.

[0064] In producing the paper feeding roller of the invention, it is preferred to modify the surface and the interior portion of the elastic member by an irradiation with radiation ray. By modifying the elastic member according to the invention, both the high paper feeding capacity over a long use and the excellent wear resistance can be realized at the same time, just as the case with the addition of organic fillers or a wear-resistant resin. The reasons why these effects are obtained are not fully clear. Presumably, the irradiation induces new cross-linking bonds at the elastomer part of the hydrogenated thermoplastic elastomer. Examples of the radiation ray useful for the radiation treatment include ultraviolet rays, electron rays and gamma rays. Electron rays are particularly efficient. These rays are radiated to the elastic member, optionally, under suitable radiating conditions depending on the kind of the ray or desired effects. In the case where electron rays are used, the preferred accelerating voltage is about 50 to 300 kV, and the irradiation dose is about 10 to 200 kGy.

[0065] Basically, the elastic member of the invention need not contain additives other than the indispensable additives mentioned above, in the hydrogenated thermoplastic elastomer. Because there is no need to add a process oil or a plasticizer, there is no problem of oil transfer to papers while the papers are fed, thus avoiding staining or slipping. It is possible, however, to add a polyolefin resin shown below or a polystyrene resin, singly or in a mixture, to control workability, heat resistance or hardness, as long as it gives no adverse effect to the operational advantage of the invention.

[0066] Examples of the polyolefin resin include: polyethylene, polypropylene, a copolymer of ethylene or propylene and α-olefin, poly(4-methyl-1-pentene), polybutene, etc.

[0067] In addition to these resins, there may be added, in a small amount which causes no bleeding out problem, a radiation reaction accelerator, a flame retardant agent, an antibacterial agent, a light stabilizer, an ultraviolet absorber, a coloring agent, an antistatic agent, a hydrolysis preventive agent, a metal inactivating agent, a viscosity creating agent, a thermoplastic elastomer, a thermoplastic adhesive resin, etc., depending on necessity.

[0068] The elastic member used for the invention requires no high temperature treatment or a vulcanizing step requiring a long time at a high temperature. Therefore, the production steps are simplified, and complex production apparatuses are not needed. In the case of irradiation which is carried out when necessary, an electron ray is used as a radiation source, enabling completion of the treatment in an extremely short time in comparison with a vulcanizing step.

[0069] The paper feeding roller of the invention can be advantageously used as one element of a paper feeding mechanism for an imaging apparatus such as a copying machine, a printer and a facsimile or other paper handling apparatuses. The invention contemplates incorporating the paper feeding roller into a paper feeding mechanism in an imaging apparatus. The paper feeding roller of the invention is used advantageously for a paper feeding mechanism which allows sheet-by-sheet feeding of papers from stacked sheet-like papers. The paper feeding mechanism using the paper feeding roller of the invention includes, but is not limited to, paper feeding mechanisms of a retardant roller type or a separation pad type.

[0070]FIG. 5 shows a schematic view of an example of a retardant roller type paper feeding mechanism in which the paper feeding roller of the invention is incorporated. According to the mechanism, the paper feeding roller 10 of the invention is positioned in a state to press papers 15 stacked on a tray(not shown). When the paper feeding step starts, the roller 10 rotates in the direction of the arrow to pick up sheets one by one, and to feed the sheets forward. The sheet 15 fed by the roller 10 is guided between a feed roller 20 and a reverse roller 30, both rotating in the directions of their arrows and fed forward. The paper feeding roller 10 of the invention may be used in place of the feed roller 20 and the reverse roller 30.

[0071]FIG. 6 shows a schematic view of an example of a separation pad type paper feeding mechanism in which the paper feeding roller of the invention is incorporated. According to the mechanism, the paper feeding roller 10 of the invention is positioned in a state to press papers 15 stacked on a tray (not shown). When the paper feeding step starts, the roller 10 rotates in the direction of the arrow to pick up sheets one by one, and to feed the sheets forward. A separation pad 16 positioned below the paper feeding roller 10 operates, in combination with the roller 10, to prevent double feeding of papers 15 and to ensure that the paper feeds forward.

[0072]FIG. 7 shows a schematic view of another example of a separation pad type paper feeding mechanism in which the paper feeding roller of the invention is incorporated. Because the mechanism is provided at a low cost, it is used in many ink jet printers. According to the mechanism, the paper feeding roller 10 of the invention is positioned in the feeding direction of the papers 15 stacked on a tray 18 in a manner to press the papers. The roller 10 has a shape of a cylinder with a portion of the curved face cut off to make a flat, whereby the circumferential length of the roller can be adjusted to meet to the length of the sheet. Therefore, a paper end sensor can be saved, resulting in reducing the production cost. When the paper feeding starts, the roller 10 rotates in the direction shown by an arrow to pick up the papers 15 one by one and to feed the papers forward. A separation pad 17 positioned below the roller 10 operates, in combination with the roller 10, to prevent double feeding of papers 15 and to ensure that the paper feeds forward, because a pressing force acts to the direction shown by an arrow.

[0073] The paper used by the paper feeding mechanism is not limited. Proper papers include, but are not limited to, generally used ordinary papers (both of domestic papers and foreign papers), coated papers, regenerated papers, drawing papers, ground wood papers, photographic papers, plastic films, etc., which are widely used by ink jet printers. That is, it should be noted that the paper feeding roller of the invention can feed any kind of paper. The roller of the invention has a high paper feeding capacity for feeding even heavy sheet of a basic weight of about 150 g/m² or heavier, for a long time. Further, it is free from the problem of a miss feeding, double feeding or paper powder accumulation.

EXAMPLES

[0074] The invention is explained by reference to working examples and comparative examples. It should naturally be understood that the invention is not limited by the examples.

Examples 1 to 22 and Comparative Examples 1 to 8

[0075] In each of the examples, commercially available starting materials shown below were used.

[0076] Hydrogenated polystyrene-based thermoplastic elastomer: SEPS2063 . . . produced by Kuraray, styrene content: 13%; SEBS G1657 . . . produced by Clayton Polymer Japan, styrene content: 13%.

[0077] Thermoplastic polyurethane elastomer: TPU660 . . . produced by Japan Miraktran, hardness: 60A.

[0078] Additives: Silica RX200 . . . globular silica (hydrophobically treated surface, average primary grain size: 12 nm), produced by Nippon Aerosil KK; Silica 200 . . . globular silica (hydrophilic surface, average primary grain size: 12 nm), produced by Nippon Aerosil KK; Silica SOC1 . . . globular silica (average grain size: 0.2 μm), produced by Tatsumori KK; Silica FS973 . . . Crushed Silica (average grain size: 22 μm), produced by Denki Kagaku Kogyo KK; Silica FB201 S . . . Melted Silica (average grain size: 22 μm), produced by Denki Kagaku Kogyo KK; Silica VN3 . . . Precipitating Method Silica (average grain size: 10 μm), produced by Nippon Silica Kogyo KK. Alumina . . . Aluminum Oxide C (average grain size: 10 μm), produced by Nippon Silica Kogyo KK. WK500 . . . Electro-conductive ceramic fiber (average grain size 5 to 15 μm), produced by Otsuka Kagaku KK. Carbon Black(CB) . . . Farness Black Sheest300, produced by Tokai Carbon KK.

[0079] Preparation of Samples

[0080] In each of the samples, the elastomer shown in Table 1 below was used to prepare a block elastomer sample. For examples where additives were used with the elastomer, the elastomer and the additives in amounts shown in Table 1 were mixed by a mixer provided by Branvender Company, under a temperature of 180° C., a rotation of 30 rpm and a mixing time of 10 minutes.

[0081] In each of Examples 1 to 22, a prepared block elastomer sample was formed to a sheet having projections. The sheets with projections were made to have either one of pattern A or B below.

[0082] Pattern A: As shown in FIG. 3, each of the projections has a cylindrical form with a height of 0.47 mm and a diameter of 0.25 mm, and is arranged with a density of 476 projections/cm².

[0083] Pattern B: As shown in FIG. 4, each of the projections has a quadrangular pyramid form with a height of 0.635 mm and a side of a quadrangle top of 0.102 mm, and is arranged with a density of 800 projections/cm².

[0084] To produce the sheet with projections, the block elastomer sample was poured into a silicone resin mold having recesses corresponding to projections, at a predetermined thickness. The upper surface of the sample was protected by Teflon™ and the sample was pressed by a press having pressing power of 200 t, to carry out press molding for 6 minutes at 205° C. After having been cooled to 65° C., the molded product was taken out from the mold. A sheet with projections having a pattern shown in Table 1 and a thickness of about 1 to 2 mm was obtained.

[0085] In Comparative Examples 1 to 8, sheets having projections beyond the scope of the invention or having no projections as shown in Table 1 were produced, for comparison. In Comparative Example 1, for example, polynorbornene was used in place of thermoplastic elastomer, a process oil was used together with a softening agent, and a flat sheet (Pattern F, about 1 to 2 mm thick) having no projections was made, to meet paper feeding rolls used for presently used printers.

[0086] After sheets with or without projections were made, surfaces of some of the sheets were irradiated with an electron beam. To carry out the irradiation, each of the sheets was adhered to a web running at a conveyor speed of 5 m/minute, guided in an electron beam irradiating apparatus with an inactive gas (nitrogen) atmosphere and an accelerating voltage of 200 kV or less, and was irradiated. The irradiation dose was 50, 100, 150 or 200 kGy, as shown in Table 1.

[0087] Evaluation Test:

[0088] The obtained sheets with or without projections were cut into pieces measuring 1 inch (2.54 cm) wide and 8 cm long. Each of the pieces was adhered to a shaft with a two-sided adhesive tape such that the projection surface of the piece was outside. For the obtained paper feeding roller, evaluating tests were made with respect to (1) elastic modulus, (2) paper feeding tension, and (3) wear resistance, in the following manner.

[0089] (1) Elastic Modulus

[0090] Separate from the samples mentioned above, other samples were prepared by similar methods. That is, 200 μm thick sheets having no projections were prepared from block elastomer samples, irradiated with an electron beam when necessary, and cut into pieces each having 10 mm wide and 35 mm long. The obtained samples were set to a dynamic, visco-elastic measuring apparatus RSAII to measure the tensioning elastic modulus E. The frequency is 1 Hz, and the strain amount is 0.5%. The obtained values are shown in Table 1.

[0091] (2) Paper Feeding Capacity

[0092] The paper feeding roller was mounted to the paper feeding part of a laser printer (trade name: “Lasershot LBP1310”, produced by Cannon, Inc). Ordinary papers (trade name: “Sun Ace RW”) were set to the tray of the printer and the paper feeding capacity was measured immediately after setting the papers. The paper feeding capacity was measured by a tensiometer (product number “FGX-5”, produced by Shimpo KK) attached to an end of the papers. The measurement was carried out five times per paper feeding roller, and the average value was treated as the paper feeding tension. The obtained results are shown in Table 1.

[0093] (3) Wear Resistance

[0094] For Examples 13, 17 and 18, the paper feeding tension was measured for the paper feeding roller after 3000 sheets had been fed. Except for the 3000 sheets that had been fed, the procedure of the above (2) paper feeding tension, was repeated. The obtained results are shown in Table 1. TABLE 1 Elastomer/ Electronic Filler ray 3000 E Tension Example Elastomer Filler (w/t parts) Pattern [kGy] papers [MPa] [g] Ex. 1 SEPS2063 SilicaSOC1 100/3 A 0 1.7 3903 Ex. 2 SEPS2063 SilicaRX200 100/3 A 0 1.9 3704 Ex. 3 SEPS2063 SilicaRX200 100/10 A 0 3 3060 Ex. 4 SEPS2063 SilicaF973 100/3 A 0 1.9 3219 Ex. 5 SEPS2063 SilicaFB201S 100/3 A 0 1.6 2997 Ex. 6 SEPS2063 Silica200 100/3 A 0 1.5 3377 Ex. 7 SEPS2063 TPU660  80/20 A 0 2.2 2901 Ex. 8 SEPS2063 TPU660  60/40 A 0 2.9 2567 Ex. 9 SEPS2063 None 100/0 A 50 3027 Ex. 10 SEPS2063 None 100/0 A 100 3139 Ex. 11 SEPS2063 None 100/0 A 150 1.5 3586 Ex. 12 SEPS2063 none 100/0 A 200 3 160 Ex. 13 SEPS2063 SilicaRX200 100/10 A 0 Done 3 2669 Ex. 14 SEPS2063 SilicaRX200 100/10 B 0 3 3438 Ex. 15 SEPS2063 100/3 B 0 1.5 4277 Ex. 16 SEBS G1657 SilicaRX200 100/3 A 0 3.9 2559 Ex. 17 SEPS2063 None 100/0 A 150 Done 1.5 3741 Ex. 18 SEPS2063 TPU660  60/40 A 0 Done 2.9 2527 Ex. 19 SEPS2063 Alumina 100/3 A 0 3.3 3349 Ex. 20 SEPS2063 WK500 100/20 A 0 3.8 3643 Ex. 21 SEPS2063 CB 100/3 A 0 1.8 3037 Ex. 22 SEPS2063 SilicaVN3 100/20 A 0 3057 C.x.1 polynorbornene Oil F 0 1 1564 C.x.2 SEPS2063 None 100/0 A 0 1.6 1701 C.x.3 SEPS2063 None 100/0 F 0 1.6 1904 C.x.4 SEPS2063 None 100/0 F 150 2376 C.x.5 SEPS2063 SOC1 100/3 F 0 1.7 300 C.x.6 TPU660 None 100/0 A 150 1263 C.x.7 TPU660 None 100/0 A 0 3.7 1015 C.x.8 TPU660 SOC1 100/3 A 0 1492

[0095] It is clear from the results shown in Table 1, that Examples 1 to 22 of the invention show remarkably better results than Comparative Examples 1 to 8.

[0096] For example, the paper feeding tension of a paper feeding roller (Control Example 2), which has projections of pattern A on its surface, which comprises only SEPS and which has received no irradiation with an electron beam, is less than 2,000 g, just as the value of the currently used paper feeding roller (no projections, Comparative Example 1).

[0097] Contrary to the above, the paper feeding tension of the roller of Examples 1 to 6, wherein silica was added, was significantly improved to approximately above 3,000 g. As is noticed also in Examples 7 and 8 where TPU was blended into SEPS, the paper feeding tension was significantly improved in comparison with each of Comparative Examples 2 and 7 (only SEPS or TPU was used).

[0098] Further, the paper feeding capacity was significantly improved for the samples of Examples 9 to 12 wherein SEPS was irradiated with an electron beam, in comparison with that of Comparative Example 2 to which no irradiation was effected. In addition, it is clearly demonstrated by Comparative Examples 6 to 8 that no effect (improvement in tension) is obtained when TPU is used with electron beam irradiation.

[0099] In Example 16, high paper feeding tension was obtained even in the case where silica was added to SEBS. In Example 17, good paper feeding tension where irradiation was made was maintained even after 3,000 sheets were fed, just as the tension for Example 11 where 3,000 sheets were not fed. In Example 18 where urethane was added to SEPS, high paper feeding tension was obtained even after 3,000 sheets were fed, just as the tension for Example 8 where 3,000 sheets were not fed. In Example 19 where alumina was added to SEPS, a high paper feeding capacity was obtained in comparison with the sample of Comparative Example 2 where no such addition was made. In Example 22 where silica was added to SEPS, a high paper feeding capacity was obtained in comparison with the sample of Comparative Example 2 where no such addition was made.

[0100] With respect to the wear resistance, Example 13 demonstrates that a high paper feeding property was obtained even after 3,000 sheets were fed.

[0101] Also the paper feeding rollers having pattern B projections showed good paper feeding tension comparable with those having pattern A projections.

[0102] The paper feeding rollers having no projections, that is, the rollers having a pattern F surface did not show a satisfactory result. For example, the rollers in Comparative Examples 3 and 4 showed low paper feeding tension although irradiated. The roller of Comparative Example 5 where silica was added caused slipping and the paper feeding tension was considerably decreased.

[0103] As has been explained in detail, the invention provides a paper feeding roller which has a high paper feeding capability, excellent wear resistance and weatherability, which maintains these features for a long time, without causing the problems of staining paper, slippage and the reduction of paper feeding capability due to paper powder adhering, and which is capable of being easily produced, and an elastic member which is effectively used with the paper feeding roller.

[0104] Further, the paper feeding roller of the invention allows sheet-by-sheet feeding of papers from a stack of sheet-like papers, without causing miss feeding, double feeding or like to a predetermined position continuously and stably, when used in a paper feeding mechanism for an imaging apparatus such as a copying machine, a printer and a facsimile. Therefore, there is provided, according to the invention, a high performance imaging apparatus which complies to the needs today.

[0105] Further, the paper feeding roller of the invention can be used for applications other than the imaging apparatuses. That is, it can be used advantageously in various apparatuses which handle stacks of papers such as automatic teller machines (ATM), cash dispensers (CD), ticketing machines and fare-adjusting machines in stations, and the like. 

What is claimed is:
 1. A paper feeding elastic member comprising a hydrogenated polystyrene-based thermoplastic elastomer, having a plurality of outwardly protruding projections on a surface of the elastic member, and satisfying at least one of the following requirements: containing an inorganic filler, containing an additive consisting of wear-resistant resin, and being modified by irradiation with radiation.
 2. The elastic member of claim 1, wherein the hydrogenated polystyrene-based thermoplastic elastomer is a hydrogenated polystyrene-based block copolymer.
 3. The elastic member of claim 1, wherein the inorganic filler is silica.
 4. The elastic member of claim 1, wherein the wear-resistant resin is a thermoplastic polyurethane resin.
 5. The elastic member of claim 1, wherein the irradiation with radiation is electron beam irradiation.
 6. The elastic member of claim 1, wherein said member is a rectangular sheet.
 7. The elastic member of claim 1, wherein said member is a cylindrical tube.
 8. The elastic member of claim 1, wherein said member is an endless belt.
 9. A paper feeding roller comprising an elastic member made from a hydrogenated polystyrene-based thermoplastic elastomer, having a plurality of outwardly protruding projections on a surface of the elastic member, and satisfying at least one of the following requirements: containing an inorganic filler, containing an additive consisting of wear-resistant resin, and being modified by irradiation with radiation.
 10. The paper feeding roller of claim 9, wherein the elastic member defines an outer peripheral surface of the paper feeding roller.
 11. The paper feeding roller of claim 9, wherein the main body of the roller is a core and the elastic member is in the form of a sheet attached to the core
 12. The paper feeding roller of claim 9, wherein the paper feeding roller allows sheet-by-sheet feeding of papers from stacked sheet-like papers in an imaging apparatus such as a copying machine, a printer and a facsimile. 